Transport Layer Security (TLS) best practices with the .NET Framework | Microsoft Docs
.NET Framework 4.7 or later defaults to using the protocols enabled by the OS.
For .NET 4.6.x, you'll have to set the
AppContext switch to
The latest - and last - version of .NET Framework is 4.8:
Download .NET (Linux, macOS, and Windows)
It's the last because the next release will be .NET 5, which is based on .NET Core. The .NET Framework isn't going anywhere, but aside from security patches it won't be updated again.
Introducing .NET 5 | .NET Blog